1. Field of the Invention
The present invention is a greenhouse heating system by means of the ground. The inconvenience of heating the ground with tubes is; the small area of heating and isolation of tubes due to dry ground around it. This can be avoided by heating the layer of soil underneath with the help of an immersed basin of gravel. Care, however, should be taken to insulate both layers with a plastic film. The porosity of the gravel permits to maintain a good quantity of water and this serves as a heating element. This has for advantage to heat the soil by an area of exchange equivalent to the area of the greenhouse. The temperature of the heating element is itself maintained at an acceptable level and does not contribute to the drying of the soil.
The bulk of heated water imprisonned in the gravel constitutes an excellent heat sink which permits the system to be less rapidly affected by heating failures.
2. Description of the Prior Art
The most simple and widespread technique to effectively heat greenhouses by means of the ground, is to incorporate tubes through which circulates hot water or steam. The ground thus heated transmits its heat to the atmosphere and assures the maintenance of ideal conditions for cultivation.
With such a system, an unusual situation has a tendancy to appear: the entire area of heat exchange being small, the temperature of the heating water should be high, which has the effect of drying the ground closest to the tubes. This dried soil acts as insulation and to continue to furnish the greenhouse with the same amount of energy, the temperature of the heating water has to be increased. The higher this temperature is increased, the more the soil will dry. This phenomenon repeats itself until the system loses its effectiveness. Moreover, this means of heating does not have enough inertia and should it fail, the temperature of the greenhouse will rapidly diminish.
Unfortunately, the prior Art has taught no satisfactory method to use thermal storage as large area heat radiator.
U.S. Pat. No. 4,286,574 issued 9/1981 to Vrolyk et Al teaches a thermal storage system. However in this system the thermal storage is not used as a heat radiator.
Foreign Pat. No. 2,278,042 issued 2/72 France to Dalle teaches a thermal storage system using plastic tubes mounted onto panel which can lay on the ground in the greenhouse floor. The thermal storage is not used as heating element (radiator) covering the floor area of the greenhouse.